1. Field of the Invention
This invention relates to a production apparatus and a production method for a barrier metal film to be formed on the surface of a substrate for eliminating the diffusion of a metal into the substrate and retaining the adhesion of the metal, when a metal film is formed on the surface of the substrate.
The present invention also relates to a metal film production method and a metal film production apparatus which can form a film of a metal, with the diffusion of the metal being eliminated and the adhesion of the metal being retained, by treating the surface of a barrier metal film produced on a substrate.
2. Description of Related Art
Semiconductors with electrical wiring have increasingly used copper as a material for the wiring in order to increase the speed of switching, decrease transmission loss, and achieve a high density. In applying the copper wiring, it has been common practice to perform the vapor phase growth method or plating on a substrate having a depression for wiring on its surface, thereby forming a copper film on the surface including the depression.
In forming the copper film on the surface of the substrate, a barrier metal film (for example, a nitride of tantalum, tungsten, titanium or silicon) is prepared beforehand on the surface of the substrate in order to eliminate the diffusion of copper into the substrate, and retain the adhesion of copper. When plating is employed, a copper shielding layer is formed on the barrier metal film by physical or chemical vapor deposition, and used also as an electrode. The barrier metal film has been formed by physical vapor deposition such as sputtering.
The depression for wiring, formed on the surface of the substrate, tends to be decreased in size, and a demand is expressed for a further reduction in the thickness of the barrier metal film. However, the barrier metal film has been produced by use of sputtering, and its directionality is not uniform. With a tiny depression on the surface of the substrate, therefore, the film is formed at the entrance of the depression before being formed in the interior of the depression, resulting in insufficient burial of the depression. Also, the substrate has been badly damaged.
Additionally, the barrier metal film is prepared for the purposes of preventing the diffusion of copper into the substrate and retaining the adhesion of copper. Hence, a nitride of tantalum, tungsten or titanium is formed as a first layer for prevention of copper diffusion, and an active metal, such as tantalum, tungsten or titanium, is formed as a second layer for retention of adhesion to copper. However, the barrier metal film is so thin that it poses difficulty at the present time in performing both functions, the prevention of copper diffusion into the substrate and the retention of copper adhesion. A demand is growing for the advent of a barrier metal film which accomplishes these two functions.
In particular, the wiring depression formed on the surface of the substrate is showing a tendency toward compactness, and further thinning of the barrier metal film is demanded. However, the necessary minimum film thickness has increased, if the barrier metal film is constructed in a two-layer structure by forming a nitride of tantalum, tungsten or titanium as a first layer for prevention of copper diffusion, and forming an active metal, such as tantalum, tungsten or titanium, as a second layer for retention of adhesion to copper.